1. Field of the Invention
The present invention generally relates to active vehicle suspension systems. More specifically, the invention relates to transmissibility shaping control for active vehicle suspension systems.
2. Description of Related Art
Generally, people all over the world drive their automobiles to various destinations. In order for these people to enjoy the ride to their destinations the suspensions systems in the automobiles must be stable and as comfortable as possible. Typically, different types of automobiles have various suspension systems, which control the ride and handling performance of the vehicle. For example, some vehicles may have a stiff suspension system that limits movement of its vehicle chassis with respect to the road wheels, but provides less isolation from rough road surfaces. In contrast to the stiff suspension system, some vehicles may have a soft suspension system that provides a more comfortable ride by isolating the vehicle occupied from the rough road surface, but allowing increased vehicle chassis movement causing a decrease in the handling performance.
These suspension systems also include various components, such as shock absorbers. Shock absorbers receive and take up shock that would normally be exerted on the wheels of the vehicle in order to improve the ride performance and the vibration of the wheels. The vibration of the wheels triggers the suspension system to vibrate in an uncontrollable manner. The suspension system vibrates at different frequencies, which may make the suspension system unstable and arduous to control. By adjusting damping with semiactive dampers, semiactive suspension system can improve ride performance, but provide limited improvement of vehicle handling.
Usually the dynamics related to vehicle suspension systems have a frequency range of up to 25 Hz, which includes two modes: vehicle body mode around 1 Hz and wheel hub mode around 11 Hz. Traditionally, the luxury vehicle suspension has soft suspension with the body mode frequency of less than 1 Hz, while sports vehicles have very stiff suspension with larger than 1 Hz body mode frequency for good handling. Generally passive suspensions are designed with a trade-off of ride comfort and handling.
Automotive OEMs and suppliers are working on active suspension systems to improve vehicle ride and handling performance. Typically active suspension systems employ hydraulic actuators and use control algorithms requiring force feedback. In addition, these systems may require up to 7.5 Kw during operation with a fully hydraulic active suspension system. The amount of power required is a significant disadvantage for implementation.
In view of the above, it is apparent that there exists a need for improved system and method for controlling active suspensions.